1. Field of the Invention
The present invention relates to a stage apparatus used on a vibration isolation table.
2. Description of the Related Art
Conventionally, in order to inspect a defect of a glass substrate of a flat panel display (FPD), a typical example of which is a liquid crystal display, a glass substrate to be inspected is placed on a stage which can be moved in two axial directions of XY. Then, while moving the stage, the surface of the glass substrate is magnified using a microscope or the like, and a defect is observed.
FIG. 11 is a structural diagram showing an example of a stage apparatus used for a defect inspection such as described above. In this apparatus, a vibration isolation table 3 having an air spring 3a and a surface plate 3b is placed on two or four support table 1. On the vibration isolation table 3, a stage 4 designed to be movable in two axial directions of XY, which cross orthogonally is mounted, and an object 5 to be examined, such as a glass substrate is to be placed on this stage 4. Further, a microscope 7 is supported on the vibration isolation table 3 by means of an arm-shaped frame 6 such that the microscope 7 is situated above the to-be-examined object 5 placed on the stage 4. With this structure, while adjusting the relative position of the object 5 with respect to the microscope 7 by moving the stage 4 in the XY directions, the surface of the object 5 can be observed with a magnified view thereof.
In the case of this structure, the stage 4 is moved in the two axial direction of XY via a ball spring 10 by means of an acceleration/deceleration device 9 such as a servo motor controlled by a control apparatus 8. Here, in the case where a servo motor is used as the acceleration/deceleration device 9, a target moving amount and a target speed are input using an input device 11, and then the input device 11 outputs the target moving amount and the target speed to the control device 8. Thus, control signals for the target moving amount and the target speed are output from the control device 8 to the acceleration/deceleration device 9, and thus the stage 4 is moved accordingly.
It should be noted here that in the case where the stage 4 is controlled full-automatically, a device which has been programmed for the motion of the stage 4 in advance, such as a computer, can be used in place of the input device 11. Further, in some cases, while the user of the apparatus monitoring an observation image taken by the microscope 7, the stage 4 is controlled manually with use of an input device such as a joystick or button switch (to be referred to as button hereinafter).
However, such a stage apparatus entails a problem that the vibration isolation table 3 is rolled due to a stress created by acceleration and deceleration of the stage 4 when it is moved by the acceleration/deceleration device 9. The stage 4 is supported on the support table 1 via the vibration isolation table 3 so that the vibration from the floor cannot be propagated to the stage 4. However, the vibration isolation table 3 has a structure in which the surface plate 3b is elastically supported by the air spring 3a. With this structure, when the acceleration/deceleration of the stage 4 is repeated on the vibration isolation stage 3, the surface plate 3b elastically supported by the air spring 3a is rolled due to a stress created each time the stage is accelerated or decelerated. When the rolling of the surface plate 3b is large, the rolling is propagated to the frame 6 which supports the microscope 7 on the surface plate 3b. This oscillation may cause a blurring of microscopic observation image.
Under these circumstances, conventionally, as a countermeasure for the rolling of the vibration isolation table, such an apparatus as disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 7-307279 is considered. This apparatus uses an active vibration isolation table, and a surface plate of this vibration isolation table is controlled with use of an actuator, in order to suppress the rolling. However, with such a means, an actuator for controlling the surface plate and a control system for the actuator are required. Therefore, the structure of the apparatus becomes complex and the production cost of the apparatus becomes high, which are not desirable.
Further, Jpn. Pat. Appln. KOKAI Publication No. 8-111374 proposes other apparatus as a countermeasure different from the above. This apparatus takes such a structure that the stress due to the acceleration or deceleration of the stage is not propagated to the vibration isolation table. That is, in this apparatus, the frame on which the acceleration/deceleration driving device for the stage is mounted is prepared as a separate member from the vibration isolation table and fixed to the floor. With this structure, the stress created while acceleration or deceleration is added only to the frame not to the vibration isolation table, and thus the rolling of the vibration isolation caused by the stress creating while acceleration or deceleration is prevented. However, with such a means, an acceleration/deceleration driving device for the stage is required. Therefore, the structure of the apparatus becomes complex and the production cost of the apparatus becomes high. Further, the contact area of the apparatus with respect to the floor becomes larger, which is not desirable.
Further, Jpn. Pat. Appln. KOKAI Publication No. 10-144601 proposes other apparatus as a countermeasure different from the above. This apparatus takes such a structure that the rolling of the vibration isolation table is suppressed with use of an order value for the acceleration/deceleration of the stage, which has been obtained by a simulation. However, with such a countermeasure, the order value is so complicated that it is not suitable for the movement of the stage having such a long stroke which, requires a time period several times larger than the rolling period of the vibration isolation table, thus creating a problem.
Therefore, the object of the present invention is to provide a stage apparatus which can effectively suppress the rolling of the vibration isolation table, caused by the stress created while accelerating or decelerating the stage.
According to the present invention, there is provided a stage apparatus including a stage mounted on a vibration isolation table, comprising: a drive unit which accelerates or decelerates the stage; an input unit which accepts a start signal of acceleration/deceleration as input data without defining a target movement amount for the stage; and a control unit which outputs an acceleration signal to the drive unit based on the data for the start of the acceleration input to the input unit and outputs, nxc3x97T seconds after the acceleration signal is output after the data for the start of deceleration is input to the input unit, and (where n represents a natural number and T represents a rolling oscillation period unique to the vibration isolation table [in seconds]), a deceleration signal having a same waveform as that of the acceleration signal and an opposite direction thereto.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.